There is no "consonant lending" here - or at least your perception of such is happening in your ear, rather than in the speakers mouth.
Here's a description from Gramadach na Gaeilge of "the Irish way of speaking":
the words of a sentence are pulled together and spoken without a pause. Pauses are almost always avoided, and some sentences seem so as if spoken as a single word. (there seems to be a quasi "horror vacui" = a fear of nothingness.)
The individual words affect each other in pronunciation (what is generally known as "Sandhi"), similar as it occurs in French (called there "liaison" , comp.: les amis [lezami]), in order to enable this unhindered flow of speech. On the other hand, in German there is a short pause made after almost every word so that the beginnings and ends of the words remain seperate and unchanged. It's important to note that those words in German beginning in a vowel actually don't begin with a vowel sound but a glottal stop, which is not the case in Irish.
What this comes down to is that the normal pronunciation of ar úsáid for an Irish speaker (not just this speaker) is "eroosawd", without a break between the words. If your brain is assigning the "r" sound to one of two separate words, that's a reflection of what your brain is used to hearing, rather than an objective assessment of what this speakers is actually saying.
Here's a direct link to the audio for this exercise - if you slow it down you can hear that there isn't any gap between the words. https://d7mj4aqfscim2.cloudfront.net/tts/ga/sentence/d5e0087907c25452d438b508d37789a2
I really, really, really wish that there was an option to slow down the speech in the exercises. I have to run them a dozen times sometimes to understand the different sounds and pull out the words on the verbal-only questions. Even then, sometimes I just have to give up and look at the answer.
Whether you can slowdown the playback at that link depends on your choice of web browser. Google Chrome doesn't support changing the playback speed (and therefore the new version of Microsoft Edge doesn't support it). Firefox allows you to slow it down, but does a very poor job of playing it back at half speed. The Legacy version of Microsoft Edge does an excellent job of playing that audio at half speed, for anyone who hasn't been upgraded yet.
The alternative is to download the audio file and play it in an app like VLC, which allows you to control playback speed.
If Google every adds support for changing playback speed, no doubt someone will develop an extension to allow you to take advantage of it.
Many words (mostly function words) have no stress of their own, they're called clitics. You have the same thing in English: unless you pronounce it very slowly and carefully, there's no difference between "about" and "a bout". And please don't refer to American English as "American", that's just wrong...