If you were a US based investor then now is maybe as good a time as any to buy the S & P 500. However, the main risk for non US based investors is currency risk.
President Trump wants to significantly devalue the USD, so even if the Dow goes up 10%, if the Dollar depreciates by 20% you will still lose heavily.
The US market is now as much a foreign exchange consideration as an equity one.
I was on the right side of the trade in 2016 after the Brexit vote when my US shares increased by 20% overnight. I've also been on the wrong side of the FX trade over the last few weeks, and it's quite painful.

The US market is what 10% or so cheaper than it was a few months back?

It's still more expensive than around 90%+ of its previous history.

Eventually valuation plays out. Change in PE is one of the three main drivers of equity returns over the long term. The others being divis and earnings growth.

I read an article earlier that earnings growth is slowing in the US. That is a big concern as its held up prices these past few years.

Political risk + slowing earnings + high valuations. mhhh...

I really like Vanguard S&P 500 ETF (VUSA), it's my largest equity holding at 6.2%

I also like Stan Weinstein's Stage Analysis (*)

I use a 52 week simple moving average as my timeframe for larger purchases in Hargreaves Lansdown. I've not done one for nearly a year but am eyeing it with funds from the 070325 Gilt maturity.

As I write, it's a grim looking VUSA chart from a Stage Analysis point of view in the weekly view

However, to scratch the itch, I do pick up 1 or 2 units of VUSA at a time in Vanguard for fun because it's free to deal twice a day.

Even that activity has slowed this month. The reason being my timeframe for very low risk Vanguard pick ups is 5 minutes and price has rejected the 52 SMA line in that timeframe loads of times this month. It's definitely stage 4 in that time frame which is the no go zone !!

As a no-information investor, price is all I do know which is why I quite enjoy the technical side of things

Many call it reading tea leaves which is fair enough - my make up is such that I enjoy it all more with something of a plan. Keeps me sane !!

* The book is Stan Weinstein - Secrets for Profiting in Bull and Bear Markets. It's an easy read and a good primer for technical analysis of charts