Q: My family emigrated from Ireland to the USA in only the 1800's, why did their name not get spelled as Dowling but as Doolin?
First off, remember your name hasn't got the wrong spelling its as 'correct' as the others! Most modern variations are variations of the old Gaelic so none are actually accurate and there are even variations on the Gaelic! We need to note that the correct spelling of anything, let alone names, is only relatively recent in our history. So, there was actually no 'reference' spelling to fall back on. Irish natives may have been given their spelling for their names at a school by a priest of Christian Brother, some of these were not even Irish (I have seen a few Italian priest's names in church records). Another aspect to to look at with immigrants to the US is the arrival procedure; if the immigration officer receining and form-filling is not of Irish origin pretty much every variant in a broad Irish brogue will sound like "Doolan".
Q: My family has always been English, from the West Country, for as far back as I can check. Is it possible we are not of Irish descent at all?
Yes, of course it is. The way to get a more definitive answer of this is probably to get a 'Y' DNA test of a male in your family. This will show that, like the rest of us, your ancesters came out of Africa. Depending on the depth of the test it could give you a highly probable route as your ancestors migrated across Europe. If it says your DNA came predominently from Ireland with a name like Dowling you could be fairly confident that it is of Irish origin. However, a common complication here is a Non-Paternity Event (NPE) which is far better descibed as 'misattributed paternity'. That is, somewhere in a Dowling line is an individual who was not a Dowling by blood. For example, they may be adopted or not actually the assumed father's son.
Q: Will a DNA test tell me the names of my Dowling ancestors?
No. It won't give you any names at all. It will give a technical result that can be compared with other people's tests by your test provider. If you have close matches with other people you may be able to make some general assumptions about origins and, if you are lucky, identify a 'Most Recent Shared Ancestor'. Now if someone you have a match with has identified a name for that person you didn't know before, you have won the family tree research lottery and deserve to celebrate. Eventually, all genealogy research, and Irish more quickly than others, will result in people for whom we have no names. At that point DNA Haplogroups is all you are left with.
Q: Why do you concentrate on Laois in Ireland?
I always accept and research Dowlings (and variations) from anywhere in the world gladly and there are thousands not from Ireland at all. However, when I start a new project I have chosen to start at what I consider 'ground zero' for Dowlings. If you check out the Distribution pages you will see that in the 1901 census the bulk of Dowlings per population are in Laois. So, I like to think I am following some kind of scientific reasoning! Eventually, the projects will step out of Laois.