I suspect you're referring to the French usage of the term "anglo saxon" to describe any country where English is spoken? I would argue that it's completely inaccurate, but I don't think "anglo celtic" is much better.

Even as a description of England, "Anglo Saxon" is not very satisfactory. England was indeed founded by the Anglo-Saxons (i.e. the Angles and Saxons (and Jutes), Germanic peoples from continental Europe who invaded and colonised the south-west of Great Britain after the withdrawal of the Roman Empire), but after the year 1066 (the invasion of the Normans) everything changed. English culture and language is based largely on a mixture of Anglo-Saxon, Norman French and Norse (the Vikings also settled large parts of England) with some British (Celtic) influence from the peoples who inhabited the area before the arrival of the Anglo-Saxons, and so cannot nowadays be described as purely Anglo-Saxon.

For other English-speaking countries, "Anglo-Saxon" is even more inaccurate. Although parts of Scotland were settled by the Anglo-Saxons, most of the country's heritage is Gaelic (in the west), British (in the south) or Norse (in the north and west), with perhaps some trace of Pictish in the north-east. Wales is British Celtic, the Anglo-Saxons were their arch enemies. Ireland never saw an Anglo-Saxon, it's a Gaelic country and the first English invaders there were Anglo-Normans. As for Canada, USA, Australia, New Zealand, South Africa, etc. the term Anglo-Saxon is meaningless, since they became English-speaking colonies centuries after the Anglo-Saxons had ceased to exist as a people, and in any case comprise a far greater mix of peoples.

I think the term "Anglo-Saxon" is useful only in a historical context. "Anglo-Celtic" doesn't mean very much at all (especially since there is much debate about whether the term "Celtic" itself has any real meaning outside of linguistics).

Could they refer to the emigrants?
I.e. the population of the US (which has a portion of Irish ancestry) and Australia (even more may be)?

Ireland has a tiny population (a few millions), and it is unique in that its population was greater then now even immediately after the Great Famine in 19 century. But there are tens of millions people with Irish ancestors around the world.

Hi 

well these are 2 very different things. Anglo Saxon is the basis of the English language and the prodiminant culture of English speaking countries. Celtic is a  different   language group and somewhat different culture (in the UK it is Welsh, Scottish and Irish). You can say Anglo Celtic in reference to culture , but the Celtic languages have had very little effect on English language.

Thank you all!