These broad arguments over whether Americans should dump steady domestic gigs to feed their soccer wanderlust and chase lavish sums overseas really can be quite silly.

Each case is different, deserving of its own shading and measurement. What’s good for Soccer Willie might be all wrong for Soccer Wonka.

Take the cases of America’s two most promising strikers, Jozy Altidore and Eddie Johnson.

Altidore has flirted with the notion of relocating to England, a move certain to crash headfirst into the work permit wall, at least for now. England’s grinder probably isn’t the ideal environment just yet for young Altidore. He’ll benefit from a season of tutelage under contemplative tactician Juan Carlos Osorio. Plus, a stateside address will facilitate participation on Bob Bradley’s national team and Peter Nowak’s Olympic squad, which could clear the deck for a European landing a year or so hence.

That’s why vague talk of moving overseas never fills in all the blanks. The “when” and the “where” are critical; variables of playing time, team style, management and individual ability to culturally assimilate all must frame the debate.

Which brings us back to Johnson.

Two years ago, rumors careened through cyberspace that Johnson definitely was headed overseas. The deal was all but done, some pundits claimed, and conventional wisdom said Johnson’s progress demanded overseas seasoning.

But he still had room to grow here, mostly in mental development. Plus, he liked being close to his new baby girl, and there were niggling injury issues. It all served to scuttle his form in MLS, and a big move for the less-than-fully focused Johnson could have quickly gone sideways.

A seriously hobbled 2006 campaign merged into a confidence-restoring 2007 one, and by the middle of last year, Porto and Derby County were showing him the money. When those deals failed to gain altitude, the path was clear for Fulham to chase yet another American, establishing Craven Cottage as home to more expeditionary Yanks than a Paris youth hostel in summertime.

Johnson’s first runabout in West London came and went Feb. 23, rather uneventfully. He replaced fellow American Clint Dempsey in the 76th minute of Fulham’s controversial 1-0 loss to West Ham.

Deployed uncomfortably on the right, Johnson tentatively swerved through about 19 minutes and might have done better on one volley from close range. He’s no long-range option in midfield, but with Fulham’s English Premier League (EPL) survival in the balance, manager Roy Hodgson clearly will consider any ol’ offensive gambit. Johnson started at the same spot in last week’s 3-0 shellacking against Man United.

Johnson’s debut with the first team didn’t answer many questions about the wisdom of this mercurial talent’s $1.5 million move. More instructive was a full 90 minutes a week earlier against Chelsea’s reserves on a bitterly cold night at Brentford’s grounds in far West London, where the Blues stage reserve matches.

Against a good, young Chelsea side that included Ben Sahar, recent Chilean signing Franco Di Santo and relative old hand Jimmy Smith, Johnson was only occasionally dangerous. And this wasn’t a case in which Fulham was outclassed, with forwards relegated to chasing scraps in absence of adequate service (the match ended in a 2-all draw).

A Fulham midfield that included former MLS standout Simon Elliott didn’t exactly supply a smorgasbord of crosses and through balls but did provide its share. In fact, Fulham took a 2-0 lead as Blues owner Roman Abramovich and manager Avram Grant watched from the stands.

Johnson announced himself early, creating one Fulham chance with a clever flick just beyond the penalty area. He found a channel about 10 minutes later, charging behind Chelsea’s back line before seeing his shot saved from a tough angle.

From there, Johnson’s night was an unmemorable mishmash of some decent touches and some that simply weren’t good enough. Before about 500 people at Brentford’s tiny grounds, wasting possession with needless giveaways will be excused by Fulham management, who clearly want the young American to succeed. Managers and teammates shouted encouragement and instruction at Johnson all evening, obviously keen to evaluate and assist.

But if he squanders those same balls during the crushing weight of an EPL relegation battle, fans at Craven Cottage won’t be so forgiving.

Johnson admitted after drawing with Chelsea’s reserves that his fitness is suffering. He did not regularly train with a side in the two months before his late January arrival. He recognizes the need to be more assertive, to make more runs and to generally increase his effect on a match.

And that’s just the point. That’s why this move became essential for Johnson’s development.

Johnson at three-quarter speed and nominal focus still could crack open MLS contests. When fully focused and motivated, he could dominate. He makes decent runs and generally finishes with authority. But those runs will require a greater sophistication and a superfueled urgency in England. His game needs more of an edge. He must embrace the EPL mentality that nothing else in life matters past those 90 minutes.

“It’s been a little tough,” he said, “running back and forth to the United States, getting my work permit settled and everything. But I’m getting settled now and getting my fitness.”

MLS could no longer provide the demanding and problematic environment that would push Johnson beyond his comfort zone. In London, the bumps in his game will be exposed weekly until he plows them level. Primarily, that first touch as a target forward remains quite average in high-level matches. He’ll sort it out and stretch himself — or he’ll be playing a lot more reserve games in the future.

Run down to Ladbrokes betting shop and book this: It wasn’t the lure of reserve matches at quaint little Brentford that prompted Johnson’s big move.

Johnson is a fellow who enjoys the trappings of stardom. He likes his bling and his haute clothing. He enjoys la dolce vita. Fair enough. But he also is shrewd enough to recognize the sweet life in London will require amplified effort. No longer will those quick bursts, the spoils of good genetics, be enough to create the requisite separation from defenders. Even the young reserves from England’s top flight are good enough to deal with Johnson’s speed. Strikers truly earn their goals in the EPL, and so too must Johnson.

It’s Johnson’s time. It’s up to him to exploit this chance.