ETF’s are considered a fine choice for the long term.
You are weighted on the US sector, but that comes down to your preference also. If you think the emerging markets are not going to outperform the US over the next 10 years, then your portfolio should reflect that, or vice versa.
Most people split it up in any way they want really.
You could be 50% USA / 10% China / 10% Japan / 10% UK / 10% Europe / 10% stocks …
Whatever floats your boat, but pay attention to the management costs and fund sizes too, just to make sure your paying a cheap management fee and are buying into large fund sized ETFs.
Nothing is forever though, anything can happen or change - always have that in mind.