I'm getting the feeling from reading this thread that Arts and Sciences are very different in the US. I can only answer for Sciences - I came from the US and have friends/colleagues there.
The research funding situation is absolutely dire. For example, funding rates at BBSRC in the UK currently hovers between 22-25%, and in the US while NSF funding rates are close at 19%, NIH funding rates are 9% (these are the two major science funders in the US).
It really is going to matter at what type of institution you end up at. An "R1" (Research 1) institution is going to expect you to hold 2-4 major grants simultaneously, and most will expect you to obtain 100% of your salary from the grants. (It might be 'written' as something like 75%, but if you want tenure, it had better be 100%). If your research area isn't funded by the NIH, it's slightly better in that you only need to obtain 'summer salary' (e.g., 25%) from your grants. You'll be quoted a salary based on 1 year, but they only pay you for 9 months of the year, so you only get 75% of that unless you can make up the rest from grants. On the other end of the scale, small teaching institutions will pay you to mostly teach (and for over the summer if you do summer school) and will be thrilled if you pull in a small charity grant that pays for consumables. Then there is a range in-between. You'll be unlikely to get an NIH grant at an undergraduate-only institution, but that is not unheard of for NSF grants. Charities fund lots of places, and many places with have Master's programmes that last 2-3 years, so this also can provide research labour.
My personal analysis is that if I go to back to the US I am going (1) only apply only for tenured positions and (2) concentrate on small undergraduate institutions, maybe with Master's programmes.
Do be aware that tenure is not the same as Professorship. They have 3 grades: Assistant Professor (=Lecturer), Associate Professor (tenured, =SL or Reader), and Full Professor (=Professor). Depending on where you are, the barrier to tenure is usually a bit higher than that for SL on the research side, and a bit lower than for Reader. The main problem is there is a 'clock' - you have 5-7 years to meet the requirements, and if you don't, you're fired (unlike in the UK where you can stay a Lecturer forever if you want). If you're already a Lecturer with some years of experience, I'd highly recommend applying to tenured positions. Many people I knew in the US 'nudged' along their tenure applications by applying to tenured posts at other Universities.
Finally, work-life balance in the US is terrible overall, but in Universities there is a bit more flexibility (like in the UK) and at least it will be what you make of it. You'll probably officially get something like 9-15 days vacation, but as an academic you can really set your own schedule. But eyebrows will be raised if you take several two-week holidays throughout the year as that will clearly not fit; people often squeeze family holidays in alongside conference and field trips.