For the first time in more than 16 years, American investors are net sellers of their own stock market. And it's not even close.

According to Reuters, U.S. investors are pulling money out of domestic stocks at the fastest pace since at least 2009, when the financial crisis was still smoldering. What's driving this exodus? A combination of fading Big Tech returns, better valuations overseas, and a growing sense that the U.S. market's premium valuation has become unjustifiable.

Here's the thing that should make you sit up: this is happening despite a weakening dollar. Normally, when the greenback drops, it makes buying foreign assets more expensive for Americans. The fact that investors are still rotating out of U.S. stocks tells you this isn't a knee-jerk reaction—it's a genuine shift in sentiment.

So where's the money going? Europe and Japan, primarily. Both markets are trading at significant discounts to the S&P 500, and both are experiencing what strategists call a "cyclical growth upswing." Translation: their economies are actually growing while being priced like they're in permanent decline.

The European Union is about to establish its Capital Market Union, which would make European stocks more accessible and liquid for global investors. If that happens, the trickle of money leaving U.S. markets could become a flood.

Now, does this mean you should dump your VOO and go all-in on European ETFs? Of course not. Long-term, U.S. stocks have outperformed pretty much everything. But if you've been 100% domestic and wondering why your portfolio has been stuck in neutral while your buddy who bought some international exposure last year is up double digits, well... now you know.

The real question is whether this is a contrarian buy signal for U.S. stocks or the beginning of a longer trend. If everyone's selling America, maybe it's time to buy? Or maybe the crowd is finally waking up to valuations that stopped making sense years ago.

One strategist quoted by Reuters noted that U.S. investors are "increasingly looking at the global landscape from a valuation perspective," flagging the cyclical growth upswing predominantly in Europe and Japan. That's Wall Street speak for: the rest of the world is cheaper and growing faster.

Either way, the "buy America" trade that worked for the last decade is officially over. The new playbook is global diversification—and the market is telling you that loud and clear.

If they can't explain why U.S. stocks deserve a 30% premium to international markets, they're probably hiding the fact that they don't.