I've posted on this so pardon if I'm repetitive. I don't mind "FC," that's used around the world. "SC," for Soccer Club, might get side-eye from Brits and Continentals, but I make no apologies for "soccer," it's perfectly cromulent as short for "association football" in a country with multiple football codes stemming from the common ancestor*.
What I mind re: using European naming conventions is mindless aping without respect for the origins. Especially since MLS, with a single-entity structure, and American sports generally, with closed leagues with "franchises" and no pro-rel, is so antithetical to the culture of English football where sides sprang organically from groups of neighbors and were voluntary associations and "clubs" in the truest sense of that word. "United" as a name often was adopted after the merger of two local clubs (Newcastle; also Sheffield, but in their case it was the Sheffield United Cricket Club that formed out of the remnants of several local cricket clubs), or takeover of foundering clubs by newly formed investor groups (Manchester, West Ham).
Wikipedia source for all of the above.
"Wanderers" was adopted by several clubs who lacked home grounds, and/or clubs who liked "the rather romantic sense of a group of travelling gentlemen who play for pleasure rather than to win - a very English sentiment, particularly in the late 19th century when most clubs were formed. So we have Wolverhampton Wanderers, Wycombe Wanderers and Bolton Wanderers."
https://english.stackexchange.com/questions/227722/why-are-some-football-clubs-known-as-wanderers
"Rovers," "Ramblers," "Nomads," and probably "Rangers," similarly. FWIW, not too different than the culture of barnstorming baseball clubs in the US around the same time period.
The story of Sheffield Wednesday getting its name because the footballers played on Wednesday when they had the day off is well known.
"AFC" or "Athletic" is straightforward, I think; also "Sporting" along the same lines.
"City," "Town," "Hamlet," "Borough," not imaginative but organic nonetheless - straightforward appeal to civic pride.
Lots of wonders in the lower leagues.
Re: vocational names like the American "Packers" or "Steelers": several sides of "Miners Welfare" - Hemsworth, Kimberely, Nostell, others. "Billiingham Synthonia," named after a fertilizer. "Bristol Telephones FC," f/k/a "Bristol Post Office Telephones." "Cray Valley Paper Mills."
Anyway. I could go on.
Point being that these are organic.
For American clubs to import them just smells like marketing. I'd rather American clubs just used American sports naming conventions. That's fine. International games adapt to local custom. When Japan started playing baseball they named teams after corporations and that's fine for their culture, and it doesn't stop hipsters from wearing their Nippon Ham Fighters jerseys around Williamsburg. Awkward hybrids like Sporting KC and Real Salt Lake just make me cringe. So do collective noun names like Revolution and Impact (although I like Charleston Battery and Chicago Fire is ok).
Now tell me who to bill this to.