1. Pabst Brewing Co. has been American-owned for longer than the existence of the telephone
Pabst Brewing Company's beginnings are semi-ancient history -- Best and Company (its former name) was pumping out barrels of brew in Milwaukee as early as 1844. For reference, Alexander Graham Bell didn't get off his lazy ass and invent the telephone 'til 1875. So yeah: this is a lot of history we're talking about here.
2. It's also way bigger than "just" PBR
If you're an out-of-touch snark-wombat who still thinks Pabst Blue Ribbon is "for hipsters", you may be thinking: who cares? The Russians can have that hipster swill. People still say "hipster", right?
But wake up, ill-informed snark-wombat! PBR is but one of about 30 beers PBC brews, and most of 'em are steeped in just as much American drinking legacy as the Blue Ribbon beer. Labels like:
Those who've made the rounds at this country's dive bars know that each of those beers is cultishly served in its respective region. In other words, it's not "just" PBR history & reputation in jeopardy. Stow the snark, wombat.
3. It's unlikely, but the operation could move
PBC operates as a contract brewer, meaning it doesn't own its own facilities, but instead leases the space & services from already-standing facilities. (The Boston Beer Company, brewer of Sam Adams, has been famously successful on this model as well.)
With corporate HQ in Los Angeles (California beer's economic output is the country's largest, by state), it'd be counterintuitive to relocate production. Even if Oasis did go that route, it almost certainly wouldn't be overseas -- too many factors to control. But, the fact is, PBC is a moveable feast.