Maasikam can be grouped (if not performed or could not be performed every month) and performed at the end, along with the year-end aaptikam, but not sodhakumbahm. Sodhakumbham is supposed to be done daily after completing the first 13 days rituals, but nowadays done once in a month, one day before the maasikam. So if the sodhkumbham was missed to be performed, it could not be done in arrears; it is left not done once and for all. Similarly oona masikam coming on 45th day, 180th day etc. also cannot be performed in arrears, once missed; they are left not done once and for all.
But there is a facility in the USA, where the apara kaaryam (rituals related to death) could be performed in the community centre (popularly known as temples). The priests in the temple help in getting that ceremony performed. That ceremony is performed without homam at the community centre. The priests also come to house and get that ceremony performed, if the karta wishes to do with homam. If you are in the USA and keen, please go to the nearest hindu temple / community centre and enquire.
