The key points are:
US tax cuts point to ongoing budget deficits around 7% of GDP, a rising trend in already very high public debt and a further rise in already record debt interest payments.
While a full-blown US public debt crisis is unlikely, this along with declining foreign investor confidence in US policy making could mean upwards pressure on US bond yields.
In the near-term shares look like they will break to new highs. But the risk of further tariff and US public debt worries driving another bout of weakness is high
It’s possible the $US is losing its ‘safe haven’ status. This means the $A may behave a bit less as a shock absorber in a crisis, meaning more pressure on the RBA to cut rates than might normally be the case.