The Trump tax cuts seem to have spurred growth well above the sub-3% ...
Here is something that everyone who runs a household or a business knows: Borrowed Money Is NOT Income.
A corollary of this is that Increased Deficit Spending is NOT Growth.
The 2018 Republican tax cuts lowered taxes on corporations and the rich. Since congress didn't lower spending, the government is essentially borrowing an extra $150 billion a year and handing it over to corporations and the rich. They now have $150 billion more to spend this year, and it counts as GDP, but it's borrowed money. $150 billion is about 0.75% of the economy. Fake growth. Also very temporary, unless Congress does the same thing again next year.
The other fake growth is the Trump Trade War. Businesses everywhere have been stocking up on supplies ahead of new tariffs. I can't find the link now, but I read recently that economists are saying this temporary effect is worth more than 1.5% of growth. When all tariffs take effect, the opposite will occur: businesses will lower their spending by an equivalent amount because they've stockpiled so much ahead of time.
So, the actual strength of the economy in 2018Q2 was 4.2% - 0.75% - 1.5% = 1.95%. About where we've been for the last decade.