tl;dr Carriers, US wise, the whole military, keeps is high budgets because Congress uses the political leverage to keep themselves in office. Large military as

tl;dr Carriers, US wise, the whole military, keeps is high budgets because Congress uses the political leverage to keep themselves in office. Large military assets like carriers are safe against other super powers simply because any conflict that would involve their loss is going to be so costly on all other fronts as to make the point moot. So while Russia and China could sink one with effort the cost long term are their best defense, simply put the economic trade issues if a conflict comes up out weighs everything else. US wise, the military branches have always had a pissing match going on. The Navy with its carriers and the air force with its manned bombers. Both technologies are either obsolete or nearing it with the advent of smarter drones; both flying and water borne; let alone combined with new artillery like rail guns and hypersonic missiles. However that pissing match is saved by both parties in Congress who use the funding to keep political power. The US could keep its peace at half the military it has and the Chiefs of Staff know it. Congress would not even let the military close bases it clearly did not need. Congress regularly has the military buy weapons it doesn't want. So combine the internal political power Congress wields with a large military establishment with one up man ship attitude between the Air Force and Navy and we are stuck with a very expensive relic of days gone past. I am not sure how much turn over is required in Congress to pare down the military. Don't get me wrong, you may seem claims they have or will cut the budget but remember the US Congress considers increases automatic and reducing the increase while still increasing constitutes a cut.