It is not non-sense. It is no longer economically viable for America to bolster the defense of Europe given the current economic relationship. Great Britain learned this first hand after they lost the American colonies. They realized they could enjoy all of the economic benefits without having to pay for the cost to defend these lands. Now, the regular base operating costs are a drop in the bucket for America, but when you factor in the long term R&D, weapons and equipment costs, and defensive systems, it's much higher. After all, bases mean nothing if you don't have stuff there. You also can't forget the operating, training, and munitions costs the US Navy absorbs by patrolling the Atlantic and Mediterranean, not to mention the actual cost of the ships themselves. Don't you realize that the US military doesn't have to be as big if it weren't stationed in Europe? This global presence does not come cheap, and costs hundreds of billions of dollars each year.
And no, I'm not advocating for an immediate pull out of Europe and an immediate downsizing of our military. All I'm trying to do is put the real costs of operating in such a geopolitical fashion. The US cannot continue to afford its massive, global military dominance along with its other problems it must tackle: Infrastructure, rising obligatory health care costs, global warming impact, deforestation and soil deprivation, and social security. We've been funding this stuff off debt, and our debt to GDP levels have tripled since 1980. It's unsustainable with some form of renegotiation. The last time it was this high was at the end of WW2.
As for attracting foreign investment, I'll give you that, but only indirectly. War is the fastest way to throw away economic progress, and maintaining peace is fantastic for prosperity. America has always been an attractive place for foreign investment, and its economic might makes it even more attractive. The internet, actually, has been a phenomenal tool for foreign investment, because it allows for greater transparency and up-to-date statistics on a company's performance.